Photoelectron spectroscopy of manganese-based Heusler alloys

Abstract

Ultraviolet-photoemission spectroscopy has been employed to investigate the valence-band electronic structures of the magnetic alloys ${\mathrm{Co}}_{2}\mathrm{MnSn},$ ${\mathrm{Cu}}_{2}\mathrm{MnAl},$ and ${\mathrm{Pd}}_{2}\mathrm{MnSn}.$The valence band of ${\mathrm{Co}}_{2}\mathrm{MnSn}$ extends to approximately 5 eV below the Fermi level with a high density of states immediately below the Fermi edge. ${\mathrm{Cu}}_{2}\mathrm{MnAl}$ and ${\mathrm{Pd}}_{2}\mathrm{MnSn}$ have valence-band widths of 6 and 7 eV, respectively, with the highest density of states lying some 3 eV below the Fermi level in each case. Photoemission measurements in the region of the Mn $3p$ threshold indicate that Mn $3d$ character extends across the full width of the valence band for all three alloys. For ${\mathrm{Pd}}_{2}\mathrm{MnSn},$ additional photoemission measurements in the region of the Pd $4d$ Cooper minimum confirm this conclusion. Modulations in photocurrent resulting from Mn $3p$-to-$3d$ resonances across the valence band of ${\mathrm{Co}}_{2}\mathrm{MnSn}$ are most intense towards the bottom of the band. This is discussed in terms of possible variations in initial-state hybridization. The experimental photoemission spectra are compared with calculated spectra derived from theoretical band structures. Although there are some differences in shape, the bandwidths of the calculated spectra agree very well with the experimental results.